The Universe of Car Audio Sources

Exploring Car Audio Beyond Car Radio

car audio sources
If you're just listening to the radio, you're missing out. Emel Yenigelen / E+ / Getty

Throughout most of the history of car audio, there were only a handful of ways to listen to music—or any audio content—on the road. In fact, AM radio was the only car audio source at all for decades after the first aftermarket head units became available in the 1930s.

The current explosion of potential car audio sources first got rolling in the 1950s, when Chrysler experimented with mobile record players, and the very first FM car radios appeared, although it was more of a slow burn at that point than the explosion we’re seeing today.

Eight tracks came around in the 1960s, followed by cassettes in the 1970s, and then CDs in the 1980s. The latter two shared space in dashboards for nearly two decades, along with AM/FM radio, and for a while, that was all you really had to worry about in terms of car audio sources.

Those days are gone.

Breaking Down Car Audio Sources

Today, the subject of car audio sources is far more complex than it ever has been. All of the old options, up to and including eight tracks, if you can believe it, are still viable, if you’re persistent enough and willing to jump through some hoops. At the same time, new, digital methods of listening to music and other content are introduced all the time.

The good news is that you can safely ignore most of the various car audio sources out there without missing out on a whole lot, and you can even go full Luddite if you want, and cling to your old tapes, although you may be surprised at some of the options that are now available to you.

In the interest of really nailing down the different car audio sources out there, it’s important to make a distinction between an audio source as a device or type of media, and the method that’s used to connect it to a head unit.

For instance, modern head units typically have multiple built-in audio sources, like an AM/FM radio and a CD player, and also include various methods of hooking up external audio sources, like Bluetooth, and RCA or TRRS auxiliary inputs.

Internal and external audio sources and their associated media are what we’re primarily concerned with here, although we’ll also touch briefly on how to connect external sources.

Legacy Car Audio Sources

There are two main legacy car audio sources that aren’t widely available anymore and one that’s right on the cusp. Eight tracks, of course, lost the battle for dashboard real estate to cassettes a long time ago, and cassettes eventually marched off into that same long night, although they hung in for much longer. Then you have CDs, which some OEMs have started to phase out in favor of mechless head units.

Media Type

OEM availability

Aftermarket availability

External device

Eight Track

No

No

Yes

Cassette Tape

No

Yes

Yes

Compact Discs

Yes

Yes

Yes

Broadcast Audio Sources

Car audio started off with AM radio as the single available audio source, and it’s still available today from both OEMs and the aftermarket, as are FM radio, satellite radio, and HD radio. Each of these broadcast audio sources can also be added to a head unit via an external tuner and some type of auxiliary connection, in the same way that you would connect an MP3 player, or any other audio device, to a head unit. Of course, AM and FM radio are still almost universally included as built-in audio sources.

Audio source

OEM availability

Aftermarket availability

External device

AM Radio

Yes

Yes

Yes

FM Radio

Yes

Yes

Yes

Satellite Radio

Yes

Yes

Yes

HD Radio

Yes

Yes

Yes

Digital Audio Sources

This is a broad category that actually has some overlap with broadcast sources since satellite and HD radio actually use digital signals. Some of these sources utilize physical media, like CDs, USB sticks, and SD cards, all of which provide ways to take your music collection on the road. Head units that are capable of playing digital formats like MP3 and WMA via CD-R/RWs allow you to burn your digital music collection to discs, while head units that have USB connections or SD card slots make the processes much easier.

Other digital audio sources, like Internet radio and cloud storage, require some type of Internet connection. Whether you use a mobile hotspot, your phone, or your car has a built-in Internet connection and Wi-Fi network, these sources provide the greatest versatility and are the easiest to use, since they provide on-the-go access to your personal music collection via the cloud or access to a variety of personalized “radio stations” or playlists.

Media type

OEM availability

Aftermarket availability

External device

CD-R/RW

Yes

Yes

Yes

USB/SD

Yes

Yes

Yes

Phone/MP3 Player

Integration available

Integration available

Yes

Internet Radio

Yes

Yes

Yes

Cloud Storage

Yes

Yes

Yes